Screening, identification and enzyme production conditions optimization of high-yield esterase Monascus

In this study, Monascus strains were isolated from Daqu, Hongqu rice and distillers' grains samples by traditional culture and separation method, and the high-yield esterase strain was screened by transparent circle method and esterase activity measurement and identified by morphologic observation and molecular biology techniques. On the basis of fermentation medium optimization, the fermentation conditions were optimized by single factor and response surface experiments using esterase activity as response value, and the substrate specificity of the esterase produced by the screened strain was investigated. The results showed that a high-yield esterase strain of Monascus XTQ was screened, with the esterase activity (43.08±0.266) U/L, which was identified as Monascus purpureus. The optimal esterase-producing liquid medium components for the strain XTQ were obtained as follows: glucose 50 g/L, beef extract 20 g/L, MgSO₄ 1 g/L, and NaH₂SO₄ 1 g/L, and the optimal fermentation conditions were as follows: pH 6.0, fermentation temperature 33.4 ℃, and rotational speed 185 r/min. Under these optimal conditions, the activity of esterase was up to (93.82±5.65) U/L, which was 2.18 times of that before optimization. The esterase produced by the strain XTQ had good selectivity for hexanoic acid, which provided a reference for the production of synthetic ethyl hexanoate esterase.